Apparatus for determining focal position of lamps



March 19, 1929. s, F, ARBUCKLE 1,706,095

APPAiQ'rus ron DETERMINING FOCAL POSITION or mums Original Filed April 18. 1922 IN VEN TOR. jflMl/Ll. E fl a/ans.

A TTORNEY5.

Patented Mar. 19, 1929.

UNITED STATES 1,706,995 PATENT OFFICE.

SAMUEL F, ARBUCKLE, 0F DETROIT, MICHIGAN, ASSIGNOR TO MONOGRAM LENS COR- PORATION, A CORPORATION OF DELAWARE.

APPARATUS FOR DETERMINING FOCAL POSITION 0F LAMPS.

Application filed April 18, 1922, Seria1 No. 555,2 76. Renewed October 22, 1928.

It is the objectof this invention to provide means for determining the exact focal position of the light bulb in a reflector of an automobile headlight in the day time regardless of the conditions or location of the automobile at the time.

Many States have passed laws relative to light regulations which require certain focal positions of the light bulb with respect to the reflector of an automobile headlight. The purpose of said regulations are to enable the driver to distinguish an object at a maximum distance in front of the vehicle and still prevent the glare of the headlight from blinding the drivers of on-coming vehiclcs. The lenses and lighting devices approved by the several States are dependent upon a certain definite focal position of the light bulb relative to the reflector, WlllCh makes it necessary for the driver of the vehicle to have the light bulb properly focused in order to be within the law. It is likewise to the interest of the driver to properly focus his light bulb for his own protection and safety and the satisfactlon derived from driving with the maximum benefits of his headlight. The particular focal position of the filament is dependent upon the particular lighting device used, said lighting device or lens, when installed, being accompanied by specific directions for adjusting the focal position of the light bulb filamentas approved by the State for use with this device.

Heretofore the focal position of the light bulb with respectto the reflector could only be arrived at in the dark, either after nightfall or in a darkened building, and the vehicle bearing the headlights must be properly positioned with respect to a horizontal plane and a vertical wall at a prescribed dis tance in front of the headlights. Inasmuch as, this particular arrangement of the vehicle could not always be possible at the time of purchasing or installing such lenses or devices, the dealer making the sale and installation and the driver do not ordinarily take the trouble to properly focus the light bulbs for the particular lens or lighting devices installed. This results in the improper deflection or diffusion of the light rays, causing the light to be unsatisfactory to the driver and to often fail to comply with the State laws, although provided with an approved lens or lighting device.

It is the object of this invention to providea simple device or devices which may be obtained and kept on hand by all dealers in lenses and lighting devices and those who do the installing, whereby the proper focal position of thelight bulb can readily be adjusted in accordance with the direction prescribed for the approved lens or lighting device. This may be done by means of such device in the day light and without disturbing the position of the vehicle.

This arrangement comprises an elongated tubular enclosurehaving one end tapered to fit over the lamp and the other end tapered to a small central aperture through which the images of the filaments maybe observed. lVithin the tubular member there are provided means for causing the images of the filament to be thrown upon a screen provided with a scale for determining the focal position thereof. This device can be readily placed upon the lamp and after observing the focus of the images the light bulb may be adjusted back and forth until the images thrown on the screen are in proper position as prescribed in the instructions accompanying the particular lens or lighting device to be installed.

Another object of the invention is to provide means whereby it may be determined if the lamp filament is in the axis of the reflector as well as the proper distance from the rear of same, so that the beam of light obtained will have its maximum intensity in the center of the same and thereby enable the device used to deflect and distribute the light, to do so more effectually.

This is shown to be true when the axis of the device is placed in line with the axis of the reflector and the diametrical line on the dial runs through the lineal axis of the projected filament images. In the case of a defective light bulb in which the filament is not in axial alignment, the diametrical line may run thru the points of the filament images but not thru the lineal axis. The bulb may then be revolved 180 which may help this condition which may be caused by a combination of a defective bulb and the improper placing of the sleeve holding same in reflector. In the other methods of focusing the beam, the correct diameter may be determined on a wall or screen, but no indication will be 'given that the beam is not of the proper distribution.

The full nature of the invention will be understood from the acctiinpanying drawings and the following description and claims.

In the drawings, Fig. 1 is a perspective view of a portion of a vehicle showing the attachment mounted on the headlamp; Fig.

2 is a central longitudinal section through position, thereon. The door and lens of the headlamp are removed and there is placed thereover the focal position determining device comprising a longitudinally extending tube 13 having a disk 14 formed on one end thereof, said disk being arranged to completely cover and fit against the forward face of the lamp casing. For securing said device to the lamp casing there is provided an adjustable shoe 16 adapted to rest on top of the lamp, said device being secured to said shoe by means of the slotted strap 17 pivoted to the center of the disk 14, whereby the center of the disk 14 may be adjusted with respect to the center of the lamp casing. Said strap is secured to the shoe 16 by means of a wing nut 18 adapted to slide in the slot of said strap for adjustment and when tight ened clamp said strap and shoe rigidly to each other. In order that the correct ad ustment may be made, said strap is calibrated in inches.

The longitudinally projecting tubular member 13 increases in diameter'as it extends outwardly, that end adj acent'the lamp being substantially half the diameter of the reflector and the outer end of said member being substantially twice the diameter of the above mentioned end, so as to prevent reflection from the sides of said member on the screen. The outer end of said member is provided with an annular flange 19 to which is clamped, by means of a plurality of clamping screws 20, a conical end member 21 having its base of a diameter equal to the end of said tubular member and being provided with a small central opening at its forward end arranged to be accommodated to the eye of the observer. The disk 14 is impervious to the light, having two holes 23 formed therein within said tubular member, said holes being substantially 9/32" in diameter.

Said holes are located diametrically opposite each other and positioned approximately 1 4' from the center of said disk. At the opposite end of said tubular member and clamped between the flange 19 and the corresponding flange of the end member 21,

there is a screen 24 of. glazed paper, cloth or glass upon which the light image may be thrown from one side and observed on the other, side. Said screen is marked off as shown in Fig. 3 with a plurality of concentric circles spaced apart andof predetermined diameters. Each of said circlesis numbered from the cent er outwardly.

By means of this arrangement the angle of projection of'rays may be obtained at a given distance from the lamp, depending upon the lengtlrof the tubular device, which in this instance is approximately 26 inches. It is,

therefore, praotical' to set lamps to give a beam spread of any required diameter at a given distance by the use of more closely drawn circles, since it follows that a divergence of a certain .distance from the focal center at 26 inches will give a certain divergence at 100 feet, which may be readily determined.

In operation, the device'is rested upon the casing of the headlamp so that the' axial center of the tubular member is positioned at the center of the reflector and extends outwardly in alignment thereto. The screen bearing the numbered circles being in position, the light is turned on and the observer, following the instructions, notes the position of the filament images upon said screen. If they are not positioned clearly thereon the light-bulb is then adjusted back and. forth until said images are brought to the position on saidscreen indicated by the instructions. The instructions necessary for the proper focusing are prescribed by the manufacturer of the lenses or lighting device being installed, and approved by the State after laboratory tests have been made with respect thereto.

To adjust the focal position of the light bulb, the device must be revolved until the diametrical line extends axially through the points of the filament images, and if that can not be done then it will be necessary to turn the lamp over 180 degrees or replace it with a new bulb. This is in order to have the lamp properly positioned within the reflector with respect to the axis thereof for causing the projected beam of light to be properly distributed.

The invention claimed is:

1. In a device of the class described, the combination with a headlamp having. a reflector and a lighting element mounted therein, of a hollow member adapted to be mounted on the front of said head lamp and to extend forwardly therefrom, and means within said member for indicating the focal positionof said element with respect to said reflector. I v

2. In a device of the class described, the combination with a headlamp having a reflector and a lighting element mounted therem, of a hollow member adapted to be mounted upon the face =of said headlamp, a

light obstructing member having an opening therein, and a screen associated with said hollow member for indicating the relative position of the image of said element with respect to said reflector.

3. In a device of the class described, the combination with a headlamphaving a re flector and a lighting element mounted therein, of means for permitting the observation of the focal position of said element with respect to said reflector, including a longitudinally extending enclosing member, means for securing one end of said member over the face of said headlamp, a disk within said member adjacent said headlamp having an opening therein through which an image of said element may be projected by said reflector, and a screen associated with said member upon which the projected image of said element may be observed.

4. In a device of the class described, the combination with a headlamp having a reflector and a lighting element mounted therein, of means for permitting the observation of the focal position of said element with respect to said reflector, including a substantially horizontally extending tubular member provided with a disk at one end thereof having a hole therein through which an image of said element may be projected by said reflector, means for securing said member over the face of said headlamp, and a calibrated screen secured within said member at the other end thereof for receiving the projected image of said element, said member being provided with a peep-hole at its outer end through which the image upon said screen may be observed.

5. In a device of the class-described, the combination with a headlamp flector and a lighting element mounted therein, of means for permitting the observation of the focal position of said element.

with respect to said reflector, including a horizontally extending tubular member, a disk at one end of said member provided with holes diametrically positioned therein through which images of be projected by said reflector, means for securing said .disk upon the headlamp, and a screen provided with annular calibrations mounted near the outer end of said member upon which the images of said element may be received, said tubular mmber being provided with a peep-hole near its outer end for permitting the observation of said images upon said screen.

6. In a dvice of the class described, thecombination with a headlamp having a reflector and a lighting element mounted.

therein, of means for permitting the observation of the focal position of said element with respect to said. reflector, including a having a re-v said element may.

horizontally extending tubular member, a disk at one end of said member provided with a plurality of holes diametrically positioned therein through which images of said element may be projected by said reflector, means for securing said disk upon the headlamp, a screen rovided with annular calibrations upon w ich' the image of said lamp may be received, and means for removably mounting sa1d screen within the opposite end of said member from said disk, said tubular member being provided with a peephole near its outer end for permitting the observation of said images upon said screen.

7. In a device of the class described, the combinationwith a headlamp having a refiector and a lighting element mounted therein, of means for permitting the observation of the focal position of said element with respect to said reflector, including a horizontally extending tubular member having a disk secured at one end thereof provided with two diametrically. opposite holes through which the images of said element may be projected by said reflector, a screen near the opposite'end of said member upon which the images of said element may be be projected from said element, a screen near the opposite end of said member upon which the images of said element carried by said beams may be observed, a str "pivotally secured to the center of sai d disk, and an adjustable shoe slidably secured to said'strap for adjustably mounting said member on said headlamp and permitting the axial alignment thereof.

9. In a device of the class described, the combination With'a lamp having a reflector and a lighting element mounted therein, of a casing positioned in front of said lamp and separable therefrom, said casing constituting a dark chamber for light rays emanating from the lighting element, and means associated witlrsaid casing for indicating the focal position of said element'with respect to said reflector.

10. In a device of the class described, the combination with a headlamp having a reflector, and a lighting element molinted therein, of a tubular inclosing member positioned in front of and separate from said' reflector and havin an axis coinciding approximately with t at of the headlamp, a

-screen associated with said'member, and

means positioned adjacent one .end of said inclosing member having a comparatively small opening therein through which the reflected image of the element may be projected by said reflector for deterinining its focal position with respect thereto.

11. In a device of the class described, the

combination with a headlamp having a reflector, and a lighting element mounted therein, of a tubular enclosing member, a

screen associated with said member in pos1- ti on on the axis of the reflector to receive the image of said element projected by said reflector, and means on said screen for indicating the angle of divergence of said projected 'mage from parallel for determining the focal position of said element with respect 'to said reflector.

12. In a device of the character described the combination with means therein to form an image, and means to receive the image adjacent one end of said member; means for. screening external'radiation from the outer side of said screen, said last mentioned means being provided with an aperture for the inspection of the screen; and meansfor attaching said tubular member .to the lam so that its axis is approximately coinci ent with that of the lamp.

14. In a device, of the class described, a lamp adjusting device adapted to be posi-. tioned detachably in front of a headlamp reflector, comprising a tubular member hav-' ing opaque side walls; a translucent screen adjacent one end of said member; means forscreening external radiationfrom the outer side of said screen, said last mentioned-means being provided with an aperture for the 1nspection of the screen; means for attaching said tubular member to the lamp so that its axis is approximately coincident with that of the lamp; and means for adjusting said tubular member laterally to bring the images on the screen of the light source of the headlamp into proper relationship with the axis of the tubular member.

L5. An apparatus for the purpose described comprising a base provided with an upright surface adapted, to be positioned in. front and at a fixed definite distance from an electric head light of an automobile by the base, means for projecting onto said upright surface images of the filament of the electric lam of the head light, and a vertically gra uated scale adjacent the image receiving surface. Y

16. Ina device of the class described, the combination with a headlamp having a reflector and a lighting element mounted therein, of a holder member adapted to be positioned in front of said reflector; an aperture plate at one end of said member; and a screen at the other end of the member.

17. A lamp focusing device comprising a box-like body, an apertured lamp mounting space in one face of the body, one of the body faces having a sighting means therein, and an image receiving means within the body adapted to receive images projected by the lamp through the aperture of the lamp mounting space, said sighting means being so located as to render the results of the functioning of the image. receiving means visible therethrough.

- w 18, In a deviceof the class described, the

-combination -With a lamp casing containing a parabolic reflector and a lamp at the focus of the reflector, of a tubular chamber; an

apertured plate at one end of said chamber adjacent to and in front of said reflector;

ber; means for facilitating observation of the screen;' and means whereby adjustment of the device is secured relative to the horizontal axis of thereflector.

In witness whereof, I have hereunto'affixed my signature.

' SAMUEL F. ARBUCKLE.

.a light screen at the other end of said cham- 

